(1) Field of the Invention
This invention relates to an active pixel sensor, APS, having a transfer gate biased such that the potential barrier between the photodiode and the storage region is not affected by the charge accumulated by the photodiode.
(2) Description of the Related Art
U.S. Pat. No. 6,025,935 to Tseng describes a mechanism to pre-charge or inject a background charge into a storage node and allow the charge to reset through the same output base-to-emitter junction. This removes the residual image and improves the photo-response linearity.
U.S. Pat. No. 5,900,623 to Tsang et al. describes an active pixel sensor using a plurality of photocells, each including a photodiode to sense illumination and a separate storage node with a stored charge that is discharged during an integration period by the photocurrent generated by the photodiode.
U.S. Pat. No. 6,566,697 B1 to Fox et al. describes a transistor coupled between a pinned photodiode and a storage node.
U.S. Pat. No. 6,501,109 B1 to Chi describes a pixel having a photodiode for light collection and a floating gated output diode for output of gate-induced-drain-leakage current to a sense amplifier. The structure is used to reduce blooming and improve image-lag performance.